A conventional barbell assembly is shown in FIG. 6 and generally includes an axle 61, two outer tubes 62, two sleeves 63 and two locking members 64. The axle 61 has two connection holes 611 respectively defined in two ends thereof. The two outer tubes 62 are respectively mounted to the two ends of the axle 61 and each outer tube 62 has a collar 621 located therein. The outer surfaces of the distal end of each of the two ends of the axle 61 are mounted by the collar 621 and a reception space 622 is defined in the inner periphery of each of the outer tubes 62. Two sleeves 63 are respectively inserted into the two outer tubes 62 and two distal ends of the two sleeves 63 respectively contact two shoulders at the inner ends of the two outer tubes 62, the two respective distal ends of the axle 61 and the two collars 621. The two locking members 64 each have an engaging portion 641 which extends through the passage 631 of the sleeve 63 corresponding thereto, the locking members 64 are respectively threadedly connected to the connection holes 611 of the axle 61. The sleeves 63 and the outer tubes 62 are soldered together from outside of the two ends of the barbell assembly as disclosed by black triangular portions.
However, the engagement between the reception spaces 622 and the sleeves 63 requires highly precision of machining due to the large contact area between the reception spaces 622 and the sleeves 63 so as to avoid from a gap between the sleeves 63 and the reception spaces 622. If the sizes of the sleeves 63 are too big for the reception spaces 622, the sleeves 63 cannot be inserted into the reception spaces 622. If the sleeves 63 are too small, a gap is defined between the sleeves 63 and the reception spaces 622. The gap may cause the sleeves 63 to be tilt relative to the axis of the axle 61, and this affects the rotation of the outer tubes 62 relative to the axle 61. Similarly, when the engaging portion 641 of each of the locking members 64 is inserted into the passage 631 of each of the sleeves 63, a proper gap is ensured to exist between the head of the locking member 64 and the sleeve 63 after the locking member 64 is fixed to the axle 61, such that the gap allows the outer tube 62 to be rotated. The gap is difficult to be controlled so that the sleeve 63 is tightly connected to the axle 61 by the locking member 64, the outer tube 62 cannot smoothly rotate. Therefore, the sleeves 63 require precisely machined. Besides, in order to prevent the sleeves 63 from being loosened when putting the barbell assembly to the floor after each lift, the sleeves 63 are soldered to the outer tubes 62, the soldering processes needs a lot of laboring and cost.
The present invention intends to provide a barbell assembly which is improves the shortcomings of the conventional barbell assembly.